Codeigniter迁移无法重新声明类 [英] Codeigniter Migration cannot redeclare class

问题描述

我正在尝试将重置功能添加到codeigniter的迁移中。下面是我的代码：

I am trying to add reset function to codeigniter's migration. Below is my code:

class Migration extends Backend_Controller {

  public function __construct()
  {
    parent::__construct();
    $this->load->library('migration');
  }

  public function index()
  {
    //...
  }

  public function reset()
  {
    $this->migration->version(1);
    $this->db->truncate('ci_sessions'); 
    $this->migration->current();
  }

}

返回错误：

Fatal error: Cannot redeclare class Migration_Create_geo_data in D:\web_projects\vProject\framework\application\migrations\002_create_geo_data.php on line 44

如果我单独运行它们，一切都很好。在一起时会出错。知道吗？

If I run them seperately, all are okay. When together it gives error. Any idea?

推荐答案

最有可能，此错误是由于将迁移设置为如果表不存在而创建的，并且

Most likely, this error is a result of setting your migrations to create tables if they do not already exist AND cache data not being updated right away.

您的迁移脚本调用 DB_forge :: create_table 方法，该方法具有两个参数。参数一是表名，参数二是可选的。这是 if_not_exists 标志。但是，默认值为false。如果将其设置为true，则仅在不存在的表中创建表。

Your Migration script calls the DB_forge::create_table method which takes two parameters. Parameter one is the table name and parameter two is optional. It is the if_not_exists flag. The default value is false however; if it is set to true tables will only be created if they do not already exist.

如果您的表是使用 if_not_exists 参数设置为 false ，缓存问题将（可能）永远不会发生：

If your tables are created with the if_not_exists parameter set to false the caching issue will (probably) never happen:

$this->dbforge->create_table('table_name');

如果使用 if_not_exists 参数创建表设置为 true ，则需要在重新加载迁移时强制更新缓存。

If tables are created with the if_not_exists parameter set to true, you will need to force the cache to update when reloading your migrations.

$this->dbforge->create_table('table_name', TRUE);

---

以下是避免此问题的几种选择：

---

Here are a couple options to avoid this issue:

1. 仅将表名作为参数发送到 create_table 方法


2. 在 migration-> version（0） data_cache ['table_names'] c>调用

1. Only send the table name as a parameter to the create_table method
2. Unset data_cache['table_names'] after the migration->version(0) call

如果选择选项2，则此方法有效：

If you choose option 2, here is a method that works:

public function reset() {
    $this->load->library('migration');

    if (!$this->migration->version(0)) {
        echo $this->migration->error_string();
    }

    // unset table cache - this will force it to update
    unset($this->db->data_cache['table_names']);

    if (!$this->migration->current()) {
        echo $this->migration->error_string();
    }
}

---

除此之外，迁移文件会自动加载并保存在会话中。
我在system / libraries / Migration.php中更改了这一行： include $ f [0]; 改为 include_once $ f [0] ;

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